Zinc oxide (ZnO) is an intrinsically n–type semiconductor, which forms Schottky junctions with a variety of metals. Understanding the origin and modulating the rectifying behavior of these junctions has been a challenge, especially for polycrystalline ZnO. In this work, we show that the addition of p–type nickel oxide (NiO) to a polycrystalline ZnO – silver (Ag) Schottky junction can lead to an enhancement in the current–voltage response. The maximum improvement is seen at around 10 mol. % NiO, beyond which, the Ohmic behavior of NiO – Ag interface dominates, and the rectification is lowered. The ZnO – NiO composites were prepared by solid–state synthesis and electrical contacts were made using silver epoxy. X– ray diffraction studies revealed limited solid solubility in both oxide lattices while scanning electron micrographs revealed a non – homogenous composite microstructure. Defects in the system were characterized by Raman and photoluminescence spectroscopies. Finally, the current–voltage behavior was found to depend on the composite composition and can be explained based on a combination of Schottky and built – in pn junctions. These Schottky diodes can be used in room temperature gas sensing applications, where the improved rectification behaviour will lead to improved sensitivity.